The increased capability of computers to store vast amounts of on-line information has led to an increasing need for efficient data classification systems. Data classification systems are especially needed for natural language texts (e.g. articles, faxes, memos, electronic mail, etc.) where information may be unstructured and unassociated with other texts. The effect of this is that users are forced to sift through the increasing amount of on-line texts to locate relevant information. Users require that classification systems provide useful information under particular circumstances and distinguish useful information from other information.